Yes, GitLab supports such a permalink. The problem is that we frequently revise Notes as we understand problems better / improve the implementation. So a reader might link to a Note from the wiki only to study an old implementation that has been superseded.
Richard > On Dec 28, 2021, at 3:52 PM, Alan & Kim Zimmerman <alan.z...@gmail.com> wrote: > > FYI, it is possible to make a "permalink" on github, which points to the code > at a specific commit. Perhaps gitlab has something similar? > > Alan > > On Tue, 28 Dec 2021 at 19:28, Richard Eisenberg <li...@richarde.dev > <mailto:li...@richarde.dev>> wrote: > We could always make a hyperlink to the source code as hosted on GitLab. But > I actually argue not to: such links would quickly become outdated, in one of > two ways: either we make a permalink, in which case the linked Note text will > become outdated; or we make a link to a particular file & line, in which case > the Note might move somewhere else. Instead, just by naming the Note title, > we have a slightly-harder-to-use link, where you use it by grepping the > source code. This is less convenient, but it will stay up-to-date. Until we > have better tooling to, say, create an HTML anchor based on a Note, I think > this is the best we can do. > > Richard > >> On Dec 28, 2021, at 12:10 PM, Benjamin Redelings >> <benjamin.redeli...@gmail.com <mailto:benjamin.redeli...@gmail.com>> wrote: >> >> I was thinking about the relationship between the wiki and the notes in the >> GHC source. >> >> Would it be possible to link directly to [compiler notes] in the GHC source >> from the wiki, using hyperlinks? Right now, I'm seeing references that look >> like: (See Note [Constraint flavours].) >> >> (I can see the motivation to include comments in the source, but I also >> think that the wiki is more discoverable than the compiler source code. So, >> in the interests of pursuing both approaches, it would be nice to be able to >> link to notes FROM the wiki. I suppose one could include a hyperlink to the >> file on github that contains the note...) >> >> I'm not sure how much web infrastructure would be required to make >> hyperlinks for notes... >> >> -BenRI >> >> On 11/8/21 5:35 AM, Simon Peyton Jones wrote: >>> Is there anywhere on the GHC wiki that explains how to interpret this >>> output, and says that the type and dictionary applications ARE there, just >>> not shown by '-ddump-tc'? >>> >>> Perhaps it would be helpful to add some basic description of what comes out >>> of the typechecker to a page like this one? (below) >>> >>> https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/compiler/hsc-main >>> <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2F-%2Fwikis%2Fcommentary%2Fcompiler%2Fhsc-main&data=04%7C01%7Csimonpj%40microsoft.com%7Cab59b17d2f394945ad1e08d9a2b96c81%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637719740212483767%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=WZL1VADZPUlaOACd58K1XZO5MzPOKrfLFMSuBD%2FGW44%3D&reserved=0> >>> Yes it would! Would you care to start such a wiki page (a new one; don’t >>> just clutter up the one you point to)? You can write down what you know. >>> Don’t worry if you aren’t 100% sure – we can correct it. And if you >>> outright don’t know, leave a “What should I say here?” note. >>> >>> "This late desugaring is somewhat unusual. It is much more common to >>> desugar the program before typechecking, or renaming, because that presents >>> the renamer and typechecker with a much smaller language to deal with. >>> However, GHC's organisation means that >>> >>> This note is now slightly out of date. We are now, very carefully, doing >>> some desugaring before typechecking. See >>> Note [Handling overloaded and rebindable constructs] in GHC.Rename.Expr >>> Note [Rebindable syntax and HsExpansion] in GHC.Hs.Expr >>> >>> You can and should point to these and similar Notes from the wiki page you >>> write. Indeed there may be some part of what you write that would be >>> better framed as Note in GHC’s source code. >>> >>> Thanks! >>> >>> Simon >>> >>> PS: I am leaving Microsoft at the end of November 2021, at which point >>> simo...@microsoft.com <mailto:simo...@microsoft.com> will cease to work. >>> Use simon.peytonjo...@gmail.com <mailto:simon.peytonjo...@gmail.com> >>> instead. (For now, it just forwards to simo...@microsoft.com >>> <mailto:simo...@microsoft.com>.) >>> >>> From: ghc-devs <ghc-devs-boun...@haskell.org> >>> <mailto:ghc-devs-boun...@haskell.org> On Behalf Of Benjamin Redelings >>> Sent: 08 November 2021 13:12 >>> To: Richard Eisenberg <li...@richarde.dev> <mailto:li...@richarde.dev> >>> Cc: ghc-devs@haskell.org <mailto:ghc-devs@haskell.org> >>> Subject: Re: Output language of typechecking pass? >>> >>> Hi, >>> >>> >>> Questions: >>> >>> 1. It seems like this separation is actually necessary, in order to apply >>> generalization only to let arguments written by the programmer, and not to >>> let bindings introduced during desugaring. Is that right? >>> >>> I don't think so. That is, if we did it all in one pass, I still think we >>> could get generalization right. >>> I guess I asked this question wrong. I mean to say, if we did the two >>> passes in the reverse order (desugaring first, followed by typechecking), >>> that would not work, right? >>> >>> As the wiki says: >>> >>> "This late desugaring is somewhat unusual. It is much more common to >>> desugar the program before typechecking, or renaming, because that presents >>> the renamer and typechecker with a much smaller language to deal with. >>> However, GHC's organisation means that >>> >>> error messages can display precisely the syntax that the user wrote; and >>> desugaring is not required to preserve type-inference properties. >>> " >>> >>> >>> 2. Does the output of type checking contain type lambdas? >>> >>> Yes. See below. >>> >>> >>> 3. Does the type checking pass determine where to add dictionary arguments? >>> >>> Yes. See below. >>> >>> >>> 4. Are there any other resources I should be looking at? >>> >>> Yes. You want to enable -fprint-typechecker-elaboration (and possible >>> -fprint-explicit-coercions). With the former, you get to see all this stuff >>> you're looking for. It's normally suppressed so that the output resembles >>> the user's code. >>> >>> I hope this helps! >>> Richard >>> Hmm... so, I think I see how this works now. I don't think >>> '-fprint-explicit-coercions' does anything here though. >>> >>> $ ghc -ddump-tc Test2.hs -fprint-typechecker-elaboration >>> >>> ... >>> >>> AbsBinds [a_a2hp] [$dNum_a2hB] >>> {Exports: [g <= g_a2hz >>> wrap: <>] >>> Exported types: g :: forall a. Num a => a -> a -> a >>> [LclId] >>> Binds: g x_aYk y_aYl = (y_aYl * x_aYk) + 1 >>> Evidence: [EvBinds{[W] $dNum_a2hs = $dNum_a2hq >>> [W] $dNum_a2hw = $dNum_a2hq >>> [W] $dNum_a2hq = $dNum_a2hB}]} >>> >>> ... >>> >>> The type and dictionary arguments are visible here (along with the evidence >>> bindings), but type and dictionary applications are only visible if you use >>> -ddump-tc-ast, which is a lot more verbose. (I don't think there is >>> another flag that shows these applications?) Since I didn't initially know >>> what "evidence" was, and there is nothing to say that a_a2hp is a type >>> lambda argument, this was pretty opaque until I managed to read the tc-ast >>> and the light went on. >>> >>> I can see now that the type and dictionary arguments are added by >>> annotating the AST. >>> >>> Is there anywhere on the GHC wiki that explains how to interpret this >>> output, and says that the type and dictionary applications ARE there, just >>> not shown by '-ddump-tc'? >>> >>> Perhaps it would be helpful to add some basic description of what comes out >>> of the typechecker to a page like this one? (below) >>> >>> https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/compiler/hsc-main >>> <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2F-%2Fwikis%2Fcommentary%2Fcompiler%2Fhsc-main&data=04%7C01%7Csimonpj%40microsoft.com%7Cab59b17d2f394945ad1e08d9a2b96c81%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637719740212483767%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=WZL1VADZPUlaOACd58K1XZO5MzPOKrfLFMSuBD%2FGW44%3D&reserved=0> >>> -BenRI >>> > > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org <mailto:ghc-devs@haskell.org> > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > <http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs>
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